Process for polymerizing ethylene glycol terephthalate



Patented Dec. 18, 1951 UNITED STATES PATENT OFFlCE No Drawing. Application September 21, 1949, Serial No. 117,077

2 Claims.

This invention relates to an improved method for the manufacture of polymeric glycol ter-' ephthalates and more particularly to such a method which employs a novel and effective by the aid of catalysts known to the art is polymerized by means of heat, the heating being carried out in the presence of a germaniumcontaining material as catalyst. The gercatalyst in the reaction mixture. 5 manium-containing material is advantageously Glycol esters of terephthalic acid in their polyadded to the reaction mxture of glycol and acid merized form have assumed practical imporor ester after the otherwise catalyzed alcoholysis tance. The ethylene glycol ester of terephthalic reaction has been completed and before the temacid, for example, prepared by the alcoholysis perature is brought up to the degree necessary reaction of a lower alkyl ester of terephthalic to effect polymerization. A number of forms of acid with ethylene glycol, may subsequently be germanium may be used, but ordinarily it will be polymerized to form a material possessing propemployed as one of its oxides or in metallic erties that adapt it for use as an industrial fiber. form. In effecting the foregoing alcoholysis and poly- In carrying out the process, the effect of merization procedures, catalysts have been various catalysts was determined by the follownecessary to accelerate the reactions and ining procedure. The desired amounts of dimethyl crease the conversions. Catalysts have heretoterephthalate and ethylene glycol were introfore been chosen particularly with reference to duced into a small distillation flask, and the the alcoholysis reaction, wherein those catalysts alcoholysis catalyst was added. The flask was effecting rapid and complete conversion and yet heated for several hours and the methanol disimparting no undesirable color to the polymer tilled over was collected, the amount formed subsequently prepared from the alcoholysis prodbeing taken as an indication of the percentage uct have been the most desirable. These catacompletion of the alcoholysis reaction. In the V lysts, however, have not always been effective preparation 'of the monomer, the vapors distillin yielding a polymer of entirely satisfactory ing over were not allowed to exceed 70-75 0., properties, particularly with respect to viscosity, and the temperatures of, the contents were mainfrom the monomeric ethylene glycol ester of tained at 2-l0-220 C. or below. The monomer terephthalic acid formed by their aid. was then introduced directly in measured .An object of the present invention is a novel amount into a polymerization tube of 25 mm. and improved process for the manufacture of outside diameter, and the polymerization catapolymeric glycol terephthalates from the prodlyst was added. The tube was provided with a net of a glycol alcoholysis of terephthalic acid side arm for distillation purposes, and a capillary or a lower alkyl ester thereof, whereby satisfacextended nearly to the bottom of the tube, tory speed of reaction is attained and a product through which pure, dry nitrogen gas was introresults that possesses a high degree of viscosity. duced. A flask was connected to the side arm A further object is such a process wherein a novel to collect the distillate, this flask being provided catalytic material is employed to accomplish the with a vacuum pump connection. The tube was improvement. A still further object is an eflecthen heated and the excess glycol distilled over. tlve catalytic polymerization of monomeric With full vacuum in the system, the contents ethylene glycol terephthalate wherein the catawere heated at 265 C. for several hours. After lyst used does not have a detrimental effect on the polymerization cycle was completed a comthe color of the finished polymer. Additional parative measurement of the color of the polymer objects will be disclosed as the invention is dewas made, and the viscosity was determined. scribed in detail in the following. Following the foregoing procedure the cata- We have found that the foregoing objects are lysts of the present invention were shown to accomplished when the monomeric gwcol tergive superior results with respect to quality of ephthalate prepared by alcoholysis of terephthe product as determined by the viscosity and thalic acid or its lower alkyl esters with a glycol the color of the polymer produced.

Alcoholysis Catalysts ar Amt. Amt, Control ggf" First P g n; Second l g fit Polymm' 0.01 0.32 0.07-0.18 0.01 Pb terephtbalete 0.01 0.64 0.38 0.01 0.01 0.34 0.01 Pb terephthalete 0.01 0.64 use 0005 0.18 0.40 001 0.03 0.29-0.35

I The amount of catalyst is expressed in per cent by weight of the glycol terephtlmlete used. After polymerization for a constant time. 1 Polymers obtained in comparable runs with the same alcoholysis catalysts but without added polymerize! tion catalyst.

The foregoing table shows that the use of sermanium dioxide is decidedly advantageous from the viewpoint of viscosity of the material after polymerization. The use of germanium dioxide is also advantageous in that the color of the finished polymer is not adversely affected thereby; in most cases the color is appreciably improved over that of polymers catalyzed by litharge (PbO), the catalyst preferred heretofore. In the determination cited in the foregoing table, where zinc was used as the alcoholysis catalyst, the color of the polymer produced was determined to be better than that of a polymer produced by the use of litharge as the sole catalyst under otherwise similar conditions.

The amount of catalyst is not a limiting factor; generally it is found desirable to employ more than 0.001% of the weight of the terephthalic acid or its ester. An amount of catalyst in excess of 0.05% will generally be unnecessary and undesirable.

The catalyst of the present invention functions in the formation of polymeric glycol terephthalates as accelerants of the reaction and as materials that allow the obtaining of a product of high viscosity that is substantially free from color.

Ethylene glycol has been used in the examples cited and will ordinarily be the preferred diol because of its availability and the desirable products obtained. Other glycols may be employed, however, of the general formula HO- CH2 n-OH where n is a number greater than 2 and not greater than 10. Such other glycols will include diethylene glycol; 2,2-dimethyl-1,4-propanediol sometimes designated pentaglycol; and the like.

Where the term lower alkyl esters is used, moreover, we intend this to include only esters of alcohols containing not more than four carbon atoms. In addition to dimethyl terephthalate, therefore. such esters as diethyl and dibutyl terephthalates are within the scope of the invention.

The invention has been described adequately in the foregoing. It will be understood, however. that many variations may be introduced in details of procedures. quantities and specific formulas of reactants, without departure from the scope of the invention We wish to be limited, therefore, only by the following claims.

We claim:

1. A process for the manufacture of polymeric ethylene glycol terephthalate, which comprises polymerizing monomeric ethylene glycol terephthalate in the presence of a catalyst taken from the class consisting of germanium and germanium oxide.

2. A process for the manufacture of a poly- .meric glycol terephthalate, which comprises polymerizing a monomeric glycol terephthalate in the presence of a catalyst taken from the class consisting of germanium and germanium oxide.

LAWRENCE ARTHUR AUSPOS. JANE BOWEN DEMPSTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,465,319 Whinfleld et a1. Mar. 22, 1949 

1. A PROCESS FOR THE MANUFACTURE OF POLYMERIC ETHYLENE GLYCOL TERAPHTHALATE, WHICH COMPRISES POLYMERIZING MONOMERIC ETHYLENE GLYCOL TEREPHTHALATE IN THE PRESENCE OF A CATALYST TAKEN FROM THE CLASS CONSISTING OF GERMANIUM AND GERMANIUM OXIDE. 